Luke Donald dropped two shots over Merion's intimidating closing holes on Friday morning, as he ultimately slotted in one shot behind Phil Mickelson after a round of 68.

The Englishman, still looking for his first major title, began the day out in front on his own at four-under par, but picked up a bogey at the trickery 16th to fall back slightly, sending him to the last level with Mickelson at the top of the leaderboard at the three-under.

He then painfully missed a three-foot putt for his par at the 18th, dropping him in behind the American heading into the second round.

Donald, resuming on the 14th, avoided out-of-bounds at each of his first two holes as he picked up valuable pars, before a lone mistake at 16. A par at the prodigiously long par-three 17th was a boost, but a disappointing three-putt at the last - something he put down to a misread of his second putt - ultimately left a slightly sour taste in the month.

"Those holes were playing long," Donald said. "Very different to yesterday. But the wind made 16 and 18 easier, so it's very disappointing to make bogeys there."

Nevertheless, it was an encouraging start from the former world No. 1.

"I think everyone thought that as soon as the course got wet it was going to play easy," he added. "The scores certainly aren't showing that. The tough holes are extremely tough. It does give you a little bit of balance with some of those shorter holes, but you really need to play those tough ones well."

Donald's playing partner, Lee Westwood, was similarly circumspect - a four at the 17th his only slip as he joined a collection of names at level-par after 18 holes, thanks in part to an impressive sand save from a bunker at the 18th.

"It's a good start," Westwood said afterwards. "I played nicely yesterday and then came out this morning and the conditions were a little bit different. So I think 70 is a good score and I'm in decent position."

Playing behind the two Brits, Tiger Woods dropped one further shot to end three-over - missing birdie openings at the 14th and 15th, before finding a treacherous spot at the 17th and settling for a four.

That left him level with Rory McIlroy, who made mistakes at 15, 17 and 18 to haemorrhage shots over the final run-in.

Woods seemed to struggle with a left arm injury during parts of Thursday's play, and reacted in anguish at least once on Friday. When asked what he felt, Woods replied: "Pain."

He then added: "But it is what it is and you move on. I got to get ready for this next round in a little bit.

"My left arm didn't feel very good on a few shots. But overall it was not too bad a round. I certainly had two three-putts and a boatload of putts and the round could have easily been under par. So that's good heading into this afternoon."

The third member of their group, Masters champion Adam Scott, began the day three-under, but slipped back after a double-bogey at the 15th. Nevertheless, at two-over the Australian is still in contention.

Donald, Westwood and Woods' group will have a quick turnaround before their second round, where they will tee off from the 11th - covering most of the same holes they have already played this morning (albeit with different tee and pin positions) before heading for Merion's front nine.

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